We propose a series of interrelated studies. In my laboratory, hypotheses will be evaluated in terms of overall ventilatory activity. During three visits each of four months duration, testing of very precise hypotheses will then be performed in Dr. Paton's laboratory using intracellular analyses. In the first visit, we will characterize changes in the membrane potentials during eupnea and gasping of medullary neurons having respiratory-modulated discharges. In eupnea, these changes throughout the respiratory cycle are defined by a complex series of excitatory and inhibitory potentials. We will evaluate the hypothesis that, in gasping, the discharge of these neurons will be defined largely or exclusively by excitatory synaptic transmission. A related hypothesis will be tested during the second visit. The changes of membrane potentials during the gasping cycle will be unaltered following a blockade of inhibitory synaptic transmission. During the third visit, we will define if a group of medullary inspiratory neurons will have changes in membrane potential typical of "pacemaker neurons." The discharge of these pacemaker neurons may underlie the neurogenesis of the gasp. In eupnea, this pacemaker discharge is superseded by a pontomedullary neuronal circuit which generates the eupneic rhythm.